Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hi , This is a common problem with GM 4 wd vehicles,it has happened to me on one of our trucks,I did have to have the transfer case module replaced,and reprogrammed at the dealer. Here is the is a service bulletin for that problem.check if your make, model and year truck are listed, the problem can be that the control module needs to be reprogramed or replaced,it needs to be checked with a factory level scan tool. I am sending a copy of the bulletin for your information. Thanks for using Just Answer,Jerry.
Some customers may comment that the 4WD/AWD indicator lights on the selector switch do not work, or the 4WD/AWD system may be inoperative and/or the service 4WD light is illuminated. The condition is typically intermittent and always occurs at key-up. Upon investigation, the technician may find DTC C0550 set.
The Transfer Case Control Module (TCCM) has not received the wake-up call during key-up and has remained in the "sleep mode".
When the TCCM is in the "sleep mode", it will not communicate with the class II bus or the Tech 2®.